Expansible chamber type radial piston engine



y 1954 T. MULLER 2,679,210

' EXPANSIBLE CHAMBER TYPE RADIAL PISTON ENGINE Filed Sept. 14; 1948 i 2Sheets-Sheet 1 IN V EN TOR.

May 25, 1954 T. MULLER EXBANSIBLE CHAMBER TYPE RADIAL PISTON ENGINEFiled Sept. 14, 1948 I 2 Sheets-Sheet 2 Patented May 25, 1954 ATENTOFFICE SIBEE CHAMBER TYPE RADIAL PISTON ENGINE Tlieodora Miiller,Wifiterthiug- Switzerland, as- Signor 'to" Schweizerische LokomotivundMaschinenfabrik; .Winterthur, Switzerland Application'septemb'er 14,1948;-SerialNo.'49,140 J Claimsipriority, application Switzerland.September 18, 1947 -My present inventionrela'testo improvements:

in "exp'ansible-chamber type engines: of the: type including a'radiatingcylindenfreciprocating"pis tons-and annutside abutment and-in particulartheconstruction of "the relief chambers provided 1 5 on' the *piston"end+faces-. The construction of the piston "heads :and of the extended"cylinder wallsi'inengines'of "such type; forms the subject: matter "ofmy tcopending application" .Ser. N 0;

It is known in'the art'to definitelyispacethe sliding surfaces offmachine iparts sliding upon each other," and 'thus'tosubtantiallyreduce the friction;- in; that a "pressure'cham-ber isrecessed '1 fromf one of the'saidsurfaceaiwhich" chamber is suppliedthrough? a throttling aperture with: a pressure fluid:

It also ;is known'in' the ;artto' use; in. engines of :the typedescribed; pressure "chambers :sup

plied :from'the.cylinderispacer Insuchrconnection;: however,- ,certain"'diflic'ulti'es "arise," iri'that forces-additional" to. the fluidpressure may arise ontherpistons in their axial""dir.ectio'ns, such asaccelerating or centrifugal forces whichmay'be.

counteracted, during the pressure stroke, but not during the suctionstroke byjmeansof'the. pressure" chamber recessed from the piston-headslidingsface, that during the;suction:stroke the pressure-fluidsupply;to"the "pressure cham-. bers from the side of; the cylinderceases; It" is? true Tthat'the, "pressure 'chamber'could :be kept underpressure also. during the suction stroke, by"- means of a special pump;which continuously pro duces' pressure fluid,'. Whicharrangement; how-'ever, results in a complicated structure'and Rd ditio'nal manufacturingcosts: But :also' when thepiston engine runsidle orunder -a slight"load,"- sufliciently high pressure also no-longer isavailable the"working space of the" engine'- cylin der'during'thepressurestrokeysothat the slide- 4:

sure chambersnf decreasing the friction: Such" provision afiords-notonlya lower weight of the entire pistons; but also the advantage that duringthepressure period the high oii-pressure is communicatedf practicallyinstantaneously, at

least'to theentire'lubricating film'on the-support .55

5Claims: (Cl. 103 -161) 2 ingfaces disposed within the pressurechambers, so that'the lubricating film during the suction period isdisplaced more slowlyfrom the said- When the .piston' engine is so"operated. that "also the suction space is under a certain slightpressure, e. g: 2-5 atm.,' there results the faces."

advantage that thefacesat idlingalso still .are

lubricated by pressure :oils, which is possible only at aless.efficient. degree when the'supporting faces are arranged outside thepressure-chambers; .Furthenthe danger of pitting of the slide faces whenthe throttling aperture is. clogged.

also is diminished.

Various forms of mypresent invention are '11- lustrated in theaccompanying drawings, in which:

Fig. 1 shows asection'. through a three-cylin? der radial. piston;engine,

Fig. 2 is. a longitudinal axial section'through'a three'cylinder radial:piston'engine having pistons of modified design. with respect .to thoseshownin Fig. 1,

Fig. 3 shows in'a larger scale; a piston accord: ingto Figil partlyinlongitudinal section,"

Fig. 4 is -a;view"of.'the.piston .head of'Fig. 3; v

in direction'of thearrowA in Fig. 3,

Fig; '5 isa longitudinal section .through a. piston'ofi'the type shownin. Fig; 2."

Fig. 6 is a'view'of the piston head of Fig. 5 in; direction .of thearrow B. in'Fig; 5.

Fig.7.? isa fragmentary sectional view of a modified piston along theline. VII-1VII of Fig. 8..

Fig. '8 is anplanview of the piston'endas seen in the direction of thearrow. B in Fig. '7.

In Figs. land 2; the cylinder block 3 of the engine, which mayoperateiaspump or motor, is mounted rotatably on the control stud 2 which isrigidlysecuredto the. .cas-ing I which block comprises .threeradiallydisposed. cylinders. In the casing I ,r further, theabutment-5 is rotatably mounted at-6 and andeccentrically-to the axis 2a of stud z. Theabutment 5 is so coupled .7 to the cylindervblock- 3 through. a follower9, in-

form of a cross-loopcoupling or universahcou- 4D pling, that the block 3and the abutment 5 always rotate at the Lsamemumber of revolutions. Onthe inside wall of the abutment 5, which may be driven throughr-the"stub shaft 5 EL: when the engineshall operate-as pump, threeplane'faces l l 'are' provided for; against each of which the head ofone piston l2 abuts by :means of atslidee shoe "or piston head I5..

In': the rigid control 'stud2; two bores 1 are provided for supplyingand delivering the working fiuid; e.-- g. in the-sense of the=-arrowsshown in Fig. 2. The cylinders situated above the horizontal medianplane of stud 2, communicate with the upper one, and the cylinders belowthe said plane with the lower one of the said two bores 4. The web 8separates the engine suction space from the pressure space.

The structure of piston I2, in which the piston and the head I5 areintegral, is shown in a larger scale in Figs. 3, 4. A shallow chamber I6is recessed from the end face of the head I5 abutting against the face II, and is supplied with pressure fluid from the cylinder interior Iiithrough the bore and the throttling aperture ZI of the piston. Thechamber is confined by the narrow annular face 23. In the chamber I6,additional supporting faces in form of six ring sectors 24 are provided,which faces fill up the pressure chamber I6 with the exception of thesix radial grooves 25, the central recess 25 and the circular groove 29.Outside the pressure chamber, the additional annular supporting face I4is provided, which is separated from the chamber I6 through the annulargroove II.

Pressure fluid flows from the pressure chamber I6 or, respectively, thegroove 29 through the narrow gap between the annular face 23 and theflattened face II into the annular groove II from which it may flowoutwardly through the grooves I8 into the interior of abutment '5 andthrough an opening 31, back into the casing I. The chamber pressure thuscannot propagate into the gap between the additional pressure face Itand the flat face II.

The piston is subject, in the direction from the cylinder space, to afluid pressure, acting onto the piston face 22, of the magnitude Fk, aswell as to an additional force C, e. g., as radially acting centrifugalforce of the piston in the engine construction according to Fig. l. Thelubricating layer between piston head I5 and plate I I should have athickness, e. g., of approximately 0.01 mm. so as to ensure fluidfriction and thus to keep the friction as small as possible. To suchend, the sum of the fluid forces tending to push away the piston head I5from the fiat face IIat a fluid pressure in in the chamber Iii-has toequal the sum of the forces tending to press the piston head I5 againstthe face I I. Fluid then will flow from the chamber It through the gapbetween the faces I I and 23, so that the pressure 121 therein, due tothe throttling of the supply at 2 I, becomes less than the pressure p inthe cylinder I9. Denoting the full circular area of the chamber I6within the annular face 23 by F1, and that of the annular face 23 by F2,the requirement is:

The area F2 is multiplied by only half the chamber pressure, since thepressure onto the face 23 drops, from the inside to the outside,approximately linearly from 101 to zero. When 101:1), the oil flow inthe lubricating layer ceases, and a semi-fluid friction occurs. Theabove equation, when dividing by p, then reads:

In order to attain fluid friction in the case of full-loadworking-pressure, the sum of the chamber area and half the marginalarea, therefore,

must exceed the sum of the piston area and the quotient from thecentrifugal force and full-load pressure. Advantageously measures aretaken for attaining such ratio at the maximum additional force Coccurring within the most common work- (iii ing range of the engine evenat a pressure less than the full-load pressure.

During the pressure stroke, the piston pressure at the said dimensioningof the relief chamber area is slightly withdrawn from the face I I,ample oil flowing between the slide faces II and 23, 24 and, to a lesserextent, onto the face I4. During the suction stroke, the relief inchamber I6 is no longer effective, and the said faces 23, 24 and I lintercept the non-compensated additional forces C. Oil then is squeezedfrom between the supporting faces 23, 24 and I4, and the oil layerbecomes thinner until the pressure rise associated with the succeedingpressure stroke arrives in the chamber I6. In this manner, provision ismade for sufliciently lubricating the faces of the piston head duringthe entire working period of the piston.

In order to ensure a sufiicient lubrication of the piston-head facesalso when the engine is slightly loaded and the pressure of the workingfluid is low, the suction side of the piston engine advantageously alsois held under a slight pressure of, e. g., from 2 to 5 atm. by means ofa special pump. In this case, of course, a greater friction on thepiston head than when the engine is more highly loaded has to be takeninto account nevertheless. When the maximum additional force C occursonly at rare intervals in operation, the faces F1 and F2 also can bemade smaller than according to the rule set forth above.

Ledges 21 provided on the abutment 5 prevent too great a rise of thepiston heads I5 from the fiat faces I I, in that these ledges engage thesaid heads from the rear. The groove Il may be omitted, in which casethe outside diameter of the head I5 and perhaps also that of the chamberIt may be reduced somewhat, since then the annular face I4 also aids theaction of the pressure chamber I6. In such case, however, when thechamber pressure is falling out, the outside supporting face M inparticular is lubricated less efilciently through the oil bath which isalways present in the rotor abutment space outside the pistons.

The structure of the piston I3 is more fully shown in Figs. 5 and 5.Such piston structure differs from the one described above, besides theadjustable spherical segment 28 inserted between piston and slide faceII, in that the enlarged piston head isguided on the cylinder, and inthat additional supporting faces no longer. are provided outside theannular face 23. The segment 28 permits balancing small deviations ofthe piston axis from the direction normal to the face II. Its sphericalseat on the piston may be relieved, at least partially, by means of apressure chamber 3|. The segment 28 is traversed by a bore 39 throughwhich the pressure chamber I6 communicates with the oil supply bore 2t2Ifrom the cylinder space IS.

The enlarged piston head 32 is guided, over the entire piston stroke, bymeans of the guide 3-3 rigidly secured to or integral with the cylinderblock 3. In the inner dead-center position of the piston, the end face35 of said guide is situated quite close to the slide face II, asindicated in Fig. 5 by the dash line.

In order to energize the pressure chamber It, the annular groove 2%,which is supplied with pressure oil from inside through the radialgrooves 25, should extend at least over of the circumference. Undercertain conditions it is of advantage to subdivide the sector-likesupporting faces 24 by means of further smaller grooves in order tofacilitate a penetration of the pressure liquid between the said faces24 and the faces H.

In order to improve the bearing capacity of the lubricating layer of thepressure-chamber center, the radial grooves '25 may be extended only fora certain distance toward the center, as shown in Figs. 7 and 8. Thesaid grooves 25 are supplied through a plurality of bores 36 from thechamber 3!. The bores 36 may be interconnected through an annular groove(not shown).

With a given fluid pressure Fk and, if such is the case, a givenadditional force C, a gap of definite depth is established between theabutment face H and the annular piston end faces ill and 23, which gaphas to be only slightly deeper than the irregularities of the said facesin order to reduce the sliding friction practically to zero. The depthof said gap tends to be constant from the following reason. When, on onehand, the gap should increase in depth, the fluid flow through and fromthe chamber I6 is increased, and thus the pressure in the latter dropsdue to the throttle 2 I, whereby the forces acting on the piston depressthe latter down to the original depth of gap. When, on the other hand,the gap is decreased and the pressure in chamber [6 increased over thatacting on the piston through the cylinder, i. e. the original depth ofgap again is re-established.

The use of pistons shown in Figs. 5 to 8 permits the adoption of thesmallest diameter for the piston head abutting against the slide face iH, of all the forms of invention described.

The width of the marginal portion 23 may be held rather small, as hasbeen proved by tests, and may preferably be made less than of thechamber radius.

The guide ledges 21 provided on the abutment 5 are engaged in a recess34, of the thickened piston and portion 32. The recess 34 may beprovided in form of a circular turned-out groove, as shown in Fig. 5, oronly in form of lateral milled grooves 38 as shown in Fig. '7. r

The pistons suitably are made of light metal with a view of diminishingthe inertia forces.

If the piston head 15 in Fig. 3 is made as long as in Fig. 5, it alsomay be better guided by means of guide lugs 33 disposed intermediate ofthe ledges 21.

In place of a liquid, one also may use a gas as working and pressureagent.

What I claim as new and desire to secure by Letters Patent is:

1. An expansible chamber typ radial piston engine comprising a housing,a rotor movable in said housing, a cylinderblock having radial cylinderseccentrically mounted in said rotor, reciprocating pistons in saidcylinders, each piston having a longitudinal bore therein and beingprovided with a head at the outer end remote from the cylinder space,flat abutment faces on said rotor providing each for sliding engagementwith one piston head, each piston head being recessed to form a pressurechamber between the head end face and the piston abutment face, saidpressure chamber being supplied with pressure fl from the cylinder spacethrough said bore in the piston, a fluid throttling means in said borenear the end thereof at the piston head face, said pressure chamberbeing arranged in the form of a circular groove having a diameter approximately equal to the piston diameter, and a plurality of ductsestablishing communication between said circular groove and thethrottling point of said pressure fluid supply bore, said ductsextending partially in the form of open radial grooves along the endface of the piston head whereby the areas of the piston head end faceintermediate the annular groove and said radial grooves form piston headsupporting faces acting as abutment pressure relief faces.

2. A fluid pump or motor as claimed in claim 1, wherein said pressurechamber is confined within an annular supporting face provided on saidhead end face, the radial width of said annular supporting face does notexceed 15 of the radius of said pressure chamber.

3. A fluid pump or motor as claimed in claim 1, wherein said pressurechamber is confined within an annular supporting face provided on saidhead end face, the sum of the area of the pressure chamber and one halfthe area of said annular supporting face are greater than the sum of theinner piston end area and the ratio between the centrifugal force actingon the piston during normal operation and a cylinder pressure which issmaller than the cylinder pressure at full load operation of the pump ormotor.

4. A fluid pump or motor comprising a cylinder block having radialcylinders, a piston operating in each cylinder, each piston including abody portion and a separate end portion at the end thereof remote of thecylinder space, said end portion being in the form of a sphericalsegment having a spherical surface fitting a spherical recess in thepiston body portion and a flat end face, a thrust member surroundingsaid cylinder block, said thrust member being provided with flatabutment faces each being in sliding engagement with the flat end faceof a spherical segment of a piston end, each piston having alongitudinal bor therein extending through the piston body portion andsaid spherical segment, the end face of the spherical segment of eachpiston being recessed to form a pressure chamber between said end faceand said abutment face on the thrust member, said pressure chamber beingsupplied with pressure fluid from the cylinder space through said borein the piston, a fluid throttling means in said bore near the endthereof at the piston head face, said pressure chamber being arranged inthe form of a circular groove having a diameter approximately equal tothe piston diameter, and a plurality of ducts establishing communicationbetween said circular groove and the throttling point of said pressurefluid supply bore, said ducts extending partially in the form of openradial grooves along the end face of the piston head whereby the areasof the piston head end face intermediate the annular groove and saidradial grooves form piston head supporting faces acting as abutmentpressure relief faces.

5. A fluid pump or motor as defined in claim 4, wherein a second fluidpressure chamber is provided between the spherical surface of saidspherical segment and the surface of the spherical recess in the bodyportion of each piston.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 388,522 .Beauchemin Aug. 28, 1888 580,838 Almond Apr. 20, 18971,398,788 Mayer Nov. 29, 1921 2,299,234 Snader et al. Oct. 20, 19422,421,846 Neuland June 10, 1947 2,483,856 Temple Oct. 4, 1949

